1. Field of the Invention
This invention relates to an improved pneumatic control system for controlling a pneumatically operated device and to an improved thermostat and set point adjuster for such a system or the like as well as to methods of making such a thermostat and set point adjuster.
2. Prior Art Statement
It is known to provide a pneumatic control system for controlling a pneumatically operated device in relation to the operation of a pneumatic signal sending thermostat and a pneumatic signal sending set point adjuster.
For example, see the following item:
(1) U.S. Pat. No. 3,693,706--Nisley et al.
It appears that the pneumatic control system of item (1) above has a comparator for respectively receiving the pneumatic signal from the thermostat and the pneumatic signal from the set point adjuster and through internal diaphragm means thereof will control the flow of pneumatic fluid between a pneumatic source and a pneumatically operated device for a heat exchanger for a transportation vehicle to set the pneumatically operated device in relation to the pneumatic signals being received by the comparator.
The set point adjuster of item (1) above has a spring acting on a valve means thereof, the force of the spring being set by manually operated adjustable setting means of the set point adjuster to set the value of the signal produced thereby.
It is also known to provide a thermostat construction having means for directing a pneumatic signal to a pneumatically operated control device to control that device in relation to the differential between the temperature sensed by the thermostat construction and the temperature setting of the adjustable temperature setting means thereof.
For example, see the following item:
(2) U.S. Pat. No. 3,221,991--Houser.
It appears that the pneumatic thermostat of item (2) above has manual means for adjusting the temperature setting of the bimetal means of the pneumatic thermostat construction, the manual means comprising a threaded relationship betweeen parts of the housing. One of the parts of the housing carries the bimetal member and another part of the housing carries the diaphragm valve means to thereby provide an adjustment therebetween which corresponds to the temperature setting for the thermostat.
The pneumatic thermostat of item (1) above also has a threaded adjusting member to set the initial force of the bimetal member thereof.
It is also known to provide a thermostat construction having pneumatically operated temperature setting means therefor with such setting means being adapted to receive a signal from a set point adjuster that has manual means for adjusting the same and a temperature sensor for changing the setting of the set point adjuster.
For example, see the following item:
(3) U.S. Pat. No. 3,263,925--Joesting.
It appears that the pneumatically operated temperature setting diaphragm of the thermostat of item (3) above forms part of the output chamber thereof and that the manual adjusting means for the set point adjuster thereof is an item separate from the temperature sensing means of the set point adjuster which changes the setting thereof upon changes in sensed temperature.